Here is the link for the "Rocket" account (actually on board the "Dublin" - I think), of hearing "Walk along, My Sally Brown" in Genoa, Italy, while tobacco from Virginia is being unloaded:

http://books.google.com/books?id=7v1IAAAAIAAJ&pg=PA102&dq=Walk+along,+my+Sally+Brown&cd=2#v=onepage&q=Walk%20along%2C%20my%20Sal

Unfortunately no words are given so we can't know for sure is this is the same "Walkalong, You Sally Brown" that Hugill got from Harding much, much later. But it does count as another variant.

There are two geographical references to San Francisco:

{1869} Richard Maitland, San Francisco (it is impossible to know whether Maitland heard/sang "Sally Brown" in San Francisco or not on that trip.
{1884} John Mason, [anchor capstan] San Francisco, CA (This is a clear identification):

http://books.google.com/books?id=JirozwWDDaMC&pg=PA66&dq=Sally+Brown+was+a+bright+mulatto&lr=&cd=8#v=onepage&q=Sally%20Brown%20w

Later Mason again mentions "Sally Brown" sung while heaving anchor on the Mersey:

http://books.google.com/books?id=JirozwWDDaMC&pg=PA118&dq=She+drinks+rum+and+chews+tobacco&lr=&cd=7#v=onepage&q=She%20drinks%20r

At least we know she was in San Francisco, even it the date is 1884.